(1) Field of the Invention
The present invention relates to lighting apparatuses with light emitting elements mounted thereon, particularly lighting apparatuses that are free to bend.
(2) Description of the Related Art
Light Emitting Diodes (hereafter referred to as LEDs) have been attracting attention as a next-generation light source for their long life spans and future possibilities of having high luminous efficacy. Also, there are ideas to use LEDs in thin-type lighting apparatuses since LEDs are more compact than light sources of the prior art. For example, there is an idea of making a columnar pillar into a lighting fixture by adhering a lighting apparatus with LEDs to the surface of the pillar, in which case, the lighting apparatus needs to bend along the surface of the pillar.
One of the problems is that when a flexible substrate is bent, the areas of the substrate where LEDs are soldered onto also bends, and then, as a result, the solder that electrically and mechanically connects LEDs with the substrate may come off. Consequently, the LEDs may be electrically disconnected from the wiring patterns, or the LEDs themselves may come apart from the substrate.
In the Japanese Laid-Open Patent Application No. 11-163412, it is suggested that a flexible substrate is reinforced by making the substrate thicker at the positioning areas of the LEDs so that those areas do not bend even when the substrate as a whole is bent. In this lighting apparatus, some areas of the substrate, on which wiring patterns are formed in advance, are made thicker and LEDs are mounted on the top surface of those thicker areas.
Generally speaking, for a lighting apparatus, LEDs are usually mounted on a substrate with high density in order to have enough quantity of light because the quantity of light from an individual LED is small. Since the lighting apparatus of the prior art does not have a system to dissipate the heat from the LEDs, a large amount of heat liberated from the LEDs that are mounted with high density would reduce the luminous efficacy and shorten the life span of the LEDs, and this means that the merits of LEDs would be lost.
Also, in the lighting apparatus of the prior art, the thicker areas of the substrate has wiring patterns and there is a problem that it is made difficult to electrically connect the wiring patterns with LEDs as they are apart from each other.